When severe weather occurs, it is often said ‘that you can see the climate changes occurring.’ However, if one looks at the meteorological data, it is difficult to discern any changes in severe or extreme weather. Obviously if there are increases in temperature, there should be an increase in warm days and a decrease in cold days over a long term. And there is some evidence that this occurred over the past 50 years.

The evidence for any changes in severe weather is very difficult to detect. Hurricanes are an example. In the 2000-2005 period there were a number of strong Atlantic Hurricanes and many believed they were the result of the warming. Since 2005, the number of hurricanes were reduced. The longest period in over a century without any category 3 hurricanes hitting the United States is now occurring.   Hurricanes appeared to increase when satellites were first started to be used to detect them in the 1980s as hurricanes that stayed over the oceans often went unreported.

The WMO in 2010 stated that global warming has not resulted in any changes in frequency or intensity of hurricanes. Further the WMO said there is no evidence that precipitation changes occurred in hurricanes. The accumulated cyclonic energy relates to the number of storms and their strength. This is shown in the next figure.   They appear to be cyclic in nature with a decrease since the mid 1990s.

Accumulated cyclonic energy for global hurricanes

The number of reported tornados increased due to better reporting and a greater population. To better understand the variability and trend in tornado frequency in the United States, NOAA examined the total number of EF-1 and stronger, as well as strong to violent tornadoes (EF-3 to EF-5 category on the Enhanced Fujita scale). These tornadoes would have likely been reported even during the decades before Doppler radar use became widespread. The bar charts indicate there has been little trend in the frequency of the stronger tornadoes over the past 55 years. In general, tornadoes are too small to be forecast on global models.

What weather events, if any , can be related to the emission of carbon dioxide or to the recent climate changes. According the IPCC AR5 report in 2014 on extremes

• There is a lack of evidence on the sign of the trend in magnitude and frequency of floods.
• There is no evidence of trends in hail and thunderstorms.
• No evidence of trends or droughts since the middle of the 20th century on a global scale.

The only severe weather that AR5 seem to indicate that increased was extreme heat waves.